Electric discharge device with improved electrode support



Aug. 9 1966 R NFREDI ETAL 3,265,919

ELECTRIC DISCHARGE DEVICE WITH IMPROVED ELECTRODE SUPPORT Original Filed May 26. 1961 INVENTORS: ROBERT E. MANFREDI PAUL KOSKOS. JOHN W. AMMENHEUSER,

THEl

ATTORNEY.

United States Patent 3,265,919 ELECTRlC DISCHARGE DEVICE WITH IMPRQVED ELECTRGDE SUPPORT Robert E. Manfredi, Rolling Hills, Califl, Paul Koskos, Maplewood, N..l., and John W. Ammenheuser, Elsmere, N.Y., assignors to General Electric Company, a corporation of New York Original application May 26, 1961, Ser. No. 112,992, new Patent No. 3,200,283, dated Aug. 10, 1965. Divided and this application Nov. 26, 1962, Ser. No. 245,345 6 flainis. (Cl. 313238) This is a division of application, Serial No. 112,992, filed May 26, 1961, now Patent No. 3,200,283.

The present invention relates to electric discharge devices and pertains more particularly to an improved electric discharge device including improved electrode mounting means.

The primary object of the present invention is to provide in an electric discharge device improved electrode mounting means whereby the device is adapted for withstanding substantial mechanical shock and vibration.

Another object of the present invention is to provide an improved planar electrode beam power device including improved cathode mounting means adapted for minimizing any tendency toward thermally-caused axial displacement of an emissive surface of the cathode and resultant undesired variations in interelectrode spacing.

Another object of the present invention is to provide an improved cathode assembly which, in addition to satisfying the above-stated objects, is particularly elfective in the usage of electromagnetic waves in the input section of UHF tubes of planar electrode construction.

Another object of the present invention is to provide an improved planar electrode device including improved electrode mounting means eliective for facilitating manufacture.

Further objects and advantages of the invention will become apparent as the following description proceeds and the features of novelty which characterize the invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

In carrying out the objects of the invention, there is provided an electric discharge device comprising an envelope structure including a stacked series of axiallyaligned ceramic insulators. Mounted in one end of the envelope is an anode electrode. Sealed between the opposed ends of adjacent insulators are a plurality of axially spaced annular metallic contact members with inner rim portions disposed internally of the envelope. The inner rim of one of the contact members serves as a reference surface adapted for being engaged by a grid assembly for thereby providing a predetermined spacing between the anode and grid assembly. Supported by and electrically connected to the inner rim of each of an adjacent pair of the contact members is a coaxial generally cylindrical resilient combined contact and detent element formed with multiple outwardly bent spring finger contacts. A

grid assembly is adapted for being held in position against A the mentioned reference surface by a detenting eifect of the bent spring fingers of one of the resilient contact elements. The spring fingers also provide an annular electrical connection between the grid assembly and one of the annular contact members sealed in the envelope wall. Bearing against the grid assembly is a cathode assembly including a conductive cathode support member having an outer cylindrical rim portion. Engaging the rim portion of the cathode support member with a detenting eifect are the bent spring fingers of the other resilient contact. A contact member axially spaced from the above-mentioned adjacent pair of contact members removably supports a retainer cup which carries a compressed coil spring which assists in biasing the cathode assembly against the grid assembly for maintaining these assemblies in desired stacked relation. The cathode assembly comprises an insulative cylinder which effects the bearing relation with the grid assembly. Additionally, the cathode assembly comprises a conductive support sleeve coaxially supported in and by the insulative cylinder. concentrically located in the support sleeve in radially spaced relation thereto is a cup-shaped emitter. Provided between the sides of the emitter and conductive support sleeve are a pair of axial-1y spaced annular straps. The straps each include circumferentially spaced indented and protruding sections which are alternately arranged and, respectively, are secured to the sides of the emitter and support sleeve. Additionally, the indented sections of one strap are vertically aligned with the protruding sections of the other strap and the protruding sections of the one strap are vertically aligned with the indented sections of the other strap. The straps provide a rugged mount for the emitter, avoid thermally caused axial displacement and serve in providing a high frequency capacitive action between the emitter and support sleeve juncture.

For a better understanding of the invention reference may be had to the accompanying drawing in which:

FIGURE 1 is an enlarged partially sectionalized view of an electric discharge device incorporating an embodiment of the invention;

FIGURE 2 is an enlarged plan view of the cathode assembly; and

FIGURE 3 is an enlarged fragmentary perspective view of the cathode assembly.

Referring to the drawing, there is shown in FIGURE 1 an electric discharge device embodying a form of the present invention and including an envelope structure generally designated 1. The envelope structure illustrated comprises a first cylindrical ceramic insulator or section 2 which supports an anode assembly generally designated 3. The anode assembly comprises an anode block 4 having an inner end sealed in and closing one end of the envelope and including a radiator structure on the external end thereof. Additionally, the inner end of the block 4 in cludes a planar active surface 5 located in the envelope. The envelope further comprises a vertically stacked coaxially aligned series of cylindrical ceramic insulators or sections including three other ceramic cylinders of the same diameter as the cylinder 2. For convenience of reference, these last-mentioned three cylinders are designated 6, 7 and 8.

Hermetically butt-sealed between the opposed ends of insulators 2 and 6 is a generally cup-like screen grid contact 10. Similarly sealed between the opposed ends of insulators 6 and 7 is a similar grid contact 12 having an outer diameter larger than that of the screen grid contact 10. And similarly sealed between the opposed ends of insulators 7 and 8 is an annular cathode contact member 13 having an outer diameter larger than that of the control grid contact 12.

The lower end of the envelope 1 is hermetically closed by a header construction comprising cylindrical insulators and annular contact members associated with a cathode heater. This portion of the envelope comprises no part of the present invention and, therefore, need not be described further.

The screen grid contact includes an inner rim portion 14 which includes an under surface adapted for serving as a reference surface, or electrode positioning stop, predeterminedly spaced from the active anode surface 5. Provided for bearing against the under surface of the rim 14 is a grid assembly generally designated 15. The grid assembly 15 can be identical to that described and claimed in co-pending application Serial No. 832,994, filed August 6, 1959, now Patent Number 3,082,339, of R. E. Manfredi entitled Electric Discharge Device and assigned to the same assignee as the present invention.

The grid assembly 15 includes a planar screen grid 16 and a planar control grid 17. Each of the grids 16 and 17 comprises a substantially thin conductive washer including a straight diametrically extending cross-bar across which are brazed a plurality of closely spaced parallel co-planar grid wires 18. Additionally, the grids 16 and 17 are separated and mutually insulated by an insulative washer 19 interposed therebetween. The grids are suitably bonded to the opposed sides of the insulative washer and, thus, a unitary grid assembly is provided.

Electrical connection to the screen grid 16 is provided through the contact 10 and its inner rim 14. Electrical connection between the contact 12 and the control grid 17 is provided by a multiple spring finger cylindrical contact member 20. The lower end of the member 20 is fitted over and is suitably conductively secured to a cylindrical rim 12 formed on the contact member 12 internally of the envelope. The cylindrical member 26 is formed of any suitable resilient material adapted for satisfactory radio frequency conduction and includes multiple individual spring fingers, as shown. Additionally, the ends of the spring fingers are outwardly bent to serve additionally as detenting or retaining elements.

The ends of the spring fingers bear against an edge of a cup-like annular conductive member 21 which fits about and makes electrical contact with the grid 17. Thus, an annular radio frequency connection is provided between the contact 12 and the grid 17 as well as centripetal and axial forces tending to hold the grid assembly centrally in place against the reference surface.

Bearing against the underside of the member 21 is a cathode assembly generally designated 22. The cathode assembly 22 includes an insulative cylinder 23 which can advantageously be formed of ceramic, a generally cylindrical cathode support'sleeve 24 including an upwardly extending inner cylindrical section 25 and a dependent outer cylindrical section 26 of greater diameter. The sleeve sections 25 and 26 are separated by a radially extending stepped portion 27 and, as seen in FIGURE 1, the stepped portion 27 is sandwiched and bonded between the ceramic cylinder 23 and a back-up ceramic washer 28.

Positioned concentrically in the support sleeve section 25 is an emitter structure including a cup-shaped member 30 having a planar active surface 31 and a cylindrical skirt 32. The emitter 36 contains a heater arrangement comprising a helically coiled filament 33 arranged in a flat spiral and sandwiched between a pair of appropriately grooved ceramic Washers 34. The ends of the filament extend from the coiled portion through the centers of the ceramic washers and are connected to heater leads 35 which extend downwardly and are appropriately electrically connected to heater contacts provided at the lower end of the tube envelope. An end plate 36 is provided for holding the heater structure in the cathode cup. Additionally, the end plate 35 carries a dependent sleeve upon which is supported a cylindrical getter element 37.

As perhaps better seen in FIGURES 2 and 3, the cathode cup 34 is held in the support sleeve by means of a pair of axially spaced annular conductive support straps 4d. The straps 40 are each formed to include a diametrically opposed pair of bail-like indented, or inwardly extending, sections 41 and a pair of bail-like protruding sections, or outwardly extending sections, 42 spaced apart from the indented sections 41. Additionally, the upper strap is rotated 90 relative to the lower strap so as .to place each indented section in the upper strap in corresponding or vertical alignment with the protruding section in the lower strap and each indented section of the lower strap in corresponding or vertical alignment with a protruding section in the upper strap, in the manner shown in FIGURE 2. Additionally, the indented sections 41 of both straps are spot welded to the skirt 32 of the cathode cup and the protruding sections 42 are similarly secured to the inner surface of the support sleeve section 25. Thus, the cathode cup is rigidly mounted at a plurality of circumferentially and axially spaced points .thereabouts, whereby it is adapted for withstanding substantial mechanical shock and vibration without breakage or alteration of the interelectrode spacing between the active surface 31 of the cathode and control grid.

Further, the straps 40 are shaped so that the sections thereof interconnecting the indented and protruding sections, and designated 43, are substantially long and are located generally midway between the walls of the oathode skirt 32 and support sleeve section 25 and in spaced relation to these elements. In this arrangement the sections 43 comprise substantially long and relatively narrow thermal paths, with the desirable results of improved cathode thermal efficiency and minimal heat transfer to the support section 25. The improved thermal efficiency minimizes the power requirements for the heater. Also, the minimal heat transfer to the section 25 from the cathode minimizes any tendency for that section to expand thermally longitudinally or axially and, therefore, serves substantially to avoid, or to minimize, thermallycaused axial displacement of the cathode and resultant undesired variations of the interelectrode spacing. Thus, the active surface 31 of the cathode undergoes minimal, if any, axial displacement between the heated and unheated states thereof which serves to avoid objectionable radio frequency drifts or variations during early operation of the tube when substantial temperature variations ordinarily occur. Additionally, the individual straps can expand thermally length-wise without affecting the position of the cathode.

The strap sections 43 serve also to provide a desired radio frequency by-passing action between the cathode cup 30 and the support sleeve 25. Specifically, the strap sections 43 represent substantial conductive areas between the cathode cup and support sleeve and, thus, provide for a radial high capacitance between the latter two elements. This increased capacitance effectively shorts out, or counteracts, any inductance of the strap with the desirable result that the region between the cathode cup and support sleeve appear as an electrical short to radio frequency currents in a resonant circuit including the cathode. Thus, the cathode mount structure provides desired radio frequency continuity to the active face of the cathode, or, in other words, constitutes a configuration particularly well adapted for the transfer of electromagnetic waves up to, and the unimpeded interaction of such electromagnetic waves with, the electron beam between the planar electrodes.

For some applications the straps 40 can be generally oval or rectangular with the emitter secured between the longer sides and the protruding end sections secured to the support sleeve. In this arrangement the protruding end sections of one strap can be rotatively displaced relative to the corresponding sections on the other strap for improving the rigidity of the structure.

Provided for electrically connecting the cathode assembly and the cathode contact 13 is a cylindrical multispring finger contact member 45 which, as seen in FIG- URE 1, is suitably supported on an inner cylindrical section 46 of the cathode contact member 13. The cylinder 45 can be generally similar to the spring finger cylinder cooperating with the grid assembly and also includes multiple outwardly bent spring fingers. The spring fingers contact the outer edge of the support sleeve section 26 and provide a suitable radio frequency connection between the cathode and cathode contact as well as centripetal and axial forces tending to hold the cathode assembly in place against the grid assembly.

The cathode assembly is also held in the position shown in FIGURE 1, in which it bears on the grid assembly 15, by a relatively large coil spring 47, the upper end of which spring bears against the outer rim of a cup-like shield element 48 between the spring and the cathode assembly directly beneath the back-up Washer 28. The lower end of the spring 47 is seated in a retaining cup 49, the center of which is apertured for extension therethrough of the filament leads 35. Provided for removably holding the retaining cup 49 in position are two pairs of detents 50 and 51, each bent out of the side wall of the retaining cup 49 and the inner ccylindrical section 46 of the cathode contact 30, respectively. The construction including the coil spring, the retaining cup and detent arrangement does not constitute part of the present invention but is disclosed and claimed in the above-identified co-pending application of R. E. Manfredi.

In manufacture, the device envelope is first fabricated including all of the above-described insulative sections, the electrode contacts, spring finger cylinders on the inner rims of the screen grid and control grid contact members, and the anode assembly, or in other words, all of the disclosed structure except the grid and cathode sub-assemblies and the lower end header construction.

The above-described grid and cathode assemblies are separately fabricated and in assembling these structures in the device the grid assembly is pushed upward until the upper surface of the control grid engages the screen grid contact inner rim 14. At this point the bent spring fingers on the control grid multiple spring finger contact cylinder 20 snap under the member 21 instead of detents to hold the grid assembly concentrically positioned and against the rim portion. During subsequent operation of the tube the spring finger contacts also serve in providing an annular highly effective radio frequency current path to the control grid. Following the described insertion of the grid assembly the cathode assembly is inserted into the position illustrated in FIGURE 1 and the spring fingers on the multiple spring finger contacts cylinder 45 snap into the illustrated position between the edge of the cathode support sleeve section 26 and serve to hold the cathode assembly in a concentric assembled position. During operation of the tube the spring fingers of the cylinder 45 serve also to provide an annular effective radio frequency current path to the cathode assembly. Following insertion of the cathode assembly the shield member 48, spring 47 and retaining cup 49 are positioned in the device and the spring 47 is compressed by exertion of an inwardly directed force on the retaining cup, following which the retaining cup is rotated into a locked position. In this manner, the grid and cathode assemblies are rigidly held in predeterminedly spaced relation in the device. Subsequently, the filament leads are suitably connected to filament contacts in the lower end header construction, that construction is sealed in place and the device is evacuated in the usual manner.

While there is shown and described a specific embodiment of the present invention, it is not desired that the invention be limited to the particular form shown and described, and it is intended by the appended claims to cover all modifications within the spirit and scope of the invention.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. An electric discharge device comprising an electrode assembly, an envelope containing said assembly and including assembly positioning means engageable by said assembly, said envelope further including an annular contact member interposed and sealed between insulative wall sections of said envelope, said annular contact member including an inner rim disposed internally of said envelope, a cylindrical multiple spring finger contact member supported coaxially in said envelope on said inner rim, and the spring fingers of said multiple spring finger contact member engaging a peripheral portion of said electrode assembly and being effective for both providing an annular conductive connection to said assembly and urging said assembly toward said assemblypositioning means.

2. An electric discharge device according to claim 1, wherein the individual spring fingers of said multiple spring finger contact are outwardly bent and engage a lower edge portion of said electrode assembly for providing both centripetal and axial forces on said electrode assembly.

3. An electric discharge device comprising an envelope, an anode mounted from one end of said envelope and including a planar active surface located in said envelope, a grid assembly contained in said envelope and comprising a stacked pair of mutually insulated planar grid elements, a plurality of annular contact members sealed in the wall of said envelope and separated by insulative sections of said wall, said annular contact member having inner rims disposed internally of said envelope, the inner rim of one of said contact members comprising a grid assembly positioning stop engageable by one of said grids, the inner rim of the next adjacent annular contact member supporting coaxially in said envelope a cylindrical multiple spring finger contact member, and the spring fingers of said multiple spring finger contact member engaging a rim portion of the other of said grid elements and being effective for both providing an annular conductive connection thereto and urging said grid assembly into engagement with said positioning stop.

4. An electric discharge device comprising an envelope, an anode mounted from one end of said envelope and including a planar active surface located in said envelope, a grid assembly contained in said envelope, means predeterminedly locating said grid assembly in predetermined spaced relation to said active surface of said anode, a cathode assembly including a planar active surface, cathode assembly positioning means engageable by said cathode assembly for predeterminedly positioning said cathode active surface relative to said grid assembly and anode surface, an anode active surface, an annular contact member sealed in the wall of said envelope, said annular contact member :having an inner rim portion disposed internally of said envelope and supporting coaxially in said envelope a cylindrical multiple spring finger contact member, and the spring fingers of said multiple spring finger contact member engaging a rim portion of said cathode assembly and being effective for both providing an annular conductive connection thereto and urging said cathode assembly in engagement with said cathode assembly positioning means.

5. An electric discharge device comprising planar anode, grid and cathode assemblies, said grid assembly comprising a stacked pair of grid elements, an envelope containing said assemblies and having said anode assembly mounted from one end thereof, said envelope having a plurality of annular contact members sealed in the wall thereof, and separated by insulative sections of said wall, said contact members having inner rim portions disposed internally of said envelope, the inner rim of one of said contact members being electrically contacted by one of said grids and further effective as a grid assembly positioning means, the inner rim of the next adjacent contact members supporting an upwardly extending cylindrical member multiple spring finger contact member conduc- 7 tively engaging a peripheral portion of the other grid element, and the inner rim of the next succeeding contact member supporting a second upwardly extending cylindrical multiple spring finger contact member, conductively contacting a peripheral portion of said cathode assembly.

6. An electric discharge device according to claim 3, wherein said cathode assembly engages said grid assembly and the ends of the spring fingers on said resilient spring finger contact member are outwardly bent and engage lower edge portions of the respective electrode assemblies for providing both centripetally and upwardly directed forces acting on said grid and cathode assemblies, thereby to retain said assemblies in coaxial, retained References Cited by the Examiner UNITED STATES PATENTS 2,379,488 7/1945 Koch et a1. 3l3292 X 3,005,123 10/1961 Griffiths 313-292 X 3,026,438 3/1962 Warne 31382 JOHN W. HUCKERT, Primary Examiner.

R. SANDLER, L. ZALMAN, I. D. KALLAM,

' Assistant Examiners. 

1. AN ELECTRIC DISCHARGE DEVICE COMPRISING AN ELECTRODE ASSEMBLY, AN ENVELOPE CONTAINING SAID ASSEMBLY AND INCLUDING ASSEMBLY POSITIONING MEANS ENGAGEABLE BY SAID ASSEMBLY, SAID ENVELOPE FURTHER INCLUDING AN ANNULAR CONTACT MEMBER INTERPOSED AND SEALED BETWEEN INSULATIVE WALL SECTIONS OF SAID ENVELOPE, SAID ANNULAR CONTACT MEMBER INCLUDING AN INNER RIM DISPOSED INTERNALLY OF SAID ENVELOPE, A CYLINDRICAL MULTIPLE SPRING FINGER CONTACT MEMBER SUPPORTED COAXIALLY IN SAID ENVELOPE ON SAID INNER RIM, AND THE SPRING FINGERS OF SAID MULTIPLE SPRING 